Conventional polyester polymer particles and pellets are typically cylindrically shaped, are solid state polymerized, and have high degrees of crystallinity. As a result, conventional pellets do not usually agglomerate in the dryers which feed an injection molding machine or an extruder. While some sticking occurs at drying temperatures (150° C. to 185° C.), the problem does not usually result in sufficient agglomeration to completely block a flow of pellets from the dryer.
We have found it advantageous to provide a polyester polymer particle which has a unique morphology and which avoids the need for solid state polymerization. This morphology includes one or more of the following features: low melt point, low degree of crystallinity, and high It.V. produced without solid state polymerization. We have discovered that these particles, if made in a conventional shape, may in some cases stick sufficiently in the dryer that mechanical agitation is required to dislodge them. We have seen that cylindrical solid stated pellets were free flowing in dryer hoppers, while in some cases cylindrical non-solid stated pellets with the unique morphology agglomerated in the pellet dryers.
This investigation would have led one to conclude that the free flowing behavior of the pellets is attributable to their morphology, and not their geometry. Our investigation continued to determine the cause for the sticking problem of these pellets. It would be desirable to provide a polyester polymer particle which minimizes agglomeration in the dryer and which has one or more of the stated characteristics.